The present invention relates to removal of underground contamination, particularly to a method of insitu decontamination using steam injection, and more particularly to a method of chemically tailoring of the steam for in situ underground mixed-waste remediation.
Cleanup of underground contamination by organics, metals, radionuclides, etc. has been a major concern, especially where the contaminated areas are located adjacent to underground water. Various approaches have been utilized to eliminate the soil contamination, often caused by leakage of fuel or oil tanks, industrial wastes, etc. These prior approaches have included physical removal (excavation) of the contaminated soil, as well as methods to flush contaminants from the soil. In many contaminated areas the contaminants are beyond the depth where excavation is possible, and fluid and steam injection used alone or coupled with soil heating has been utilized to remove the contaminants. One of the more recent approaches to solving this problem is a steam injection/subatmospheric pressure removal system disclosed in U.S. Pat. No. 5,018,576 issued May 28, 1991 to K. S. Udell et al. for the rapid cleanup of underground organics.
However, many of the contaminated areas or spills also contain mixed-waste, i.e., metals, radionuclides and organics. There is no known prior method to clean such spills or contaminated areas if they are beyond the depth where excavation is possible.
This problem is solved by the present invention which involves the simultaneous remediation of underground contamination by mixed-waste composed of organic materials and metals or radionuclides. The method of this invention utilizes steam injection in combination with injection of gases or chemicals which mobilize the mixed-waste as steam pushes the waste through the ground toward an extraction well where the waste is withdrawn by subatmospheric pressure, or immobilize waste such as metals into large clusters to prevent migration.